[map_identity]: recognize tuple identity function

[y21]

Fixes #7189

This lint now recognizes .map(|(a, b)| (a, b)) as a useless map call.

changelog: [map_identity]: recognize tuple identity function

[rustbot]

r? @llogiq

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[llogiq]

Now it should not lint on type-ascribing identities, otherwise looks good.

[y21]

Now it should not lint on type-ascribing identities, otherwise looks good.

My other PR #11521 should do this, right? Would it make sense to get that in first?

[llogiq]

With #11521 merged, this should be merge-worthy.

@bors r+

[bors]

📌 Commit a78c53a has been approved by llogiq

It is now in the queue for this repository.

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout issue7189 (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self issue7189 --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging tests/ui/map_identity.stderr
Auto-merging tests/ui/map_identity.rs
CONFLICT (content): Merge conflict in tests/ui/map_identity.rs
Auto-merging tests/ui/map_identity.fixed
CONFLICT (content): Merge conflict in tests/ui/map_identity.fixed
Auto-merging lintcheck/src/main.rs
Auto-merging clippy_utils/src/lib.rs
CONFLICT (content): Merge conflict in clippy_utils/src/lib.rs
Automatic merge failed; fix conflicts and then commit the result.

[y21]

Yeah, I knew these conflicts were gonna happen :D will fix them in a couple hours.

[bors]

☔ The latest upstream changes (presumably #11521) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #11694) made this pull request unmergeable. Please resolve the merge conflicts.

[llogiq]

@bors delegate+

[bors]

✌️ @y21, you can now approve this pull request!

If @llogiq told you to "r=me" after making some further change, please make that change, then do @bors r=@llogiq

[y21]

Rebased.
@bors r=llogiq

[bors]

📌 Commit d6fc606 has been approved by llogiq

It is now in the queue for this repository.

[bors]

⌛ Testing commit d6fc606 with merge 56c8235...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 56c8235 to master...